Material design and package-level reliability of a novel low-temperature solder based on intermetallic-compound phases with superior high-homologous temperature properties

A novel low-temperature solder which consists entirely of two phases of intermetallic compounds is developed as a reliable low-temperature interconnect. The new solder can be reflowed below 125C and yet exhibits excellent mechanical properties at homologous temperatures exceeding 0.9. Specifically, the new solder exhibits creep resistance an order of magnitude greater than conventional low-temperature solders, and the strength retention ability exceeding that of Sn-4%Ag-0.5%Cu (SAC405) at the same homologous temperatures. The mixture of two intermetallic compounds also exhibit extensive ductility comparable to conventional solders at room-temperature. Dramatic enhancement of wettability is achieved with addition of active metals via reactive wetting mechanisms. The new alloy exhibits excellent thermo-mechanical fatigue resistance with <5% failure after 1000 cycles and shock performance superior to SAC405.